(1)当n∈N*时,Sn=2an-2n,①则当n≥2,n∈N*时,Sn-1=2an-1-2(n-1).②
①-②,得an=2an-2an-1-2,即an=2an-1+2,∴an+2=2(an-1+2)∴
=2.
an+2
an?1+2
当n=1 时,S1=2a1-2,则a1=2,当n=2时,a2=6,∴{an+2}是以a1+2为首项,以2为公比的等比数列.
∴an+2=4?2n-1,∴an=2n+1-2,(7分)
(2)由bn=log2(an+2)=log22n+1=n+1,得
=bn
an+2
,n+1 2n+1
则Tn=
+2 22
+…+3 23
,③n+1 2n+1
Tn=1 2
+…+2 23
+n 2n+1
,④n+1 2n+2
③-④,得
Tn=1 2
+2 22
+1 23
+…+1 24
?1 2n+1
n+1 2n+2
=
+1 4
?
(1?1 4
)1 2n 1?
1 2
n+1 2n+2
=
+1 4
?1 2
?1 2n+1
n+1